Hand-held cellular phones have caused significant interference with navigation systems in commercial aircraft. While the power level on a cellular phone may be adjusted down to as low as six milliwatts for perfect connections, the power output can rise to as much as 2 watts. A hazard nearly as important in preventing that of interference with aircraft navigation is the potential paralysis of the ground-base cellular system. The ground-base cellular system is designed for people driving or moving slowly on the ground and assumes that each user is only able to communicate with a handful of antennas. These antenna locations then agree which one has the strongest signal from the user and then carry the communication. An individual in an aircraft flying over a city could literally tie up one channel each in over a hundred antennas and this could cause a great deal of inefficiency and near paralysis in the ground cellular system. For this reason, and for the concern about aircraft navigation, it is a violation of federal law to use a cell phone in an aircraft.
Nevertheless, our society has grown so accustomed to the use of the cellular phones that aircraft passengers frequently use them illegally in flight. The rules on the ground have been relaxed to the point now that most airlines will allow the use of the cellular phone until the aircraft doors are actually closed. Many passengers assume that this indicates that the rules are just another bit of bureaucracy and are beginning to ignore them in flight with potentially disastrous consequences. Importantly, many passengers simply forget to turn their phones off when they board the plane.
Unfortunately, in spite of the hazard to the aircraft safety and ground communication systems, no commercial aircraft at present have a system for detecting the cellular phone usage and no one has taught a system for locating the cellular phone in the aircraft. If a cellular phone transmission could be detected, it is still now impossible to decide which of a 200-400 passengers is using the phonexe2x80x94especially when one is using one of the hand-free earpieces which are essentially invisible or look like a radio earpiece.
What is needed is a system for detecting the use of a cellular phone during any time in a flight and immediately giving a location so the crew can take measures to have the cellular phone turned off.
In addition, a means is necessary for locating laptop computers, which are xe2x80x9cnoisyxe2x80x9d emitters. Some laptop computers, typically due to modifications and peripherals, can emit significant levels of broad band electromagnetic interference (EMI).
There are many patents teaching various methods of locating a cellular phone. Representative are U.S. Pat. No. 5,512,908 of Herrick, xe2x80x9cApparatus and method for locating cellular telephones,xe2x80x9d and Dunn (U.S. Pat. No. 5,873,040), xe2x80x9cWireless 911 emergency location.xe2x80x9d All of the location techniques have a common goal of locating an emergency call from a cellular phone and are designed to give a location within several hundred feet. These inventions would clearly not be useful in an aircraft as the total dimensions of a plane are within this limit of resolution.
Other similar patents such as Herrick (U.S. Pat. No. 5,625,364), xe2x80x9cApparatus and method for finding a signal emission sourcexe2x80x9d are doubly inappropriate for use in an aircraft, as they require moving the antenna to use phase changes to triangulate to the source.
A very interesting patent is Jones (U.S. Pat. No. 5,670,742); xe2x80x9cEMI protected aircraft.xe2x80x9d Jones teaches the use of shielding in the aircraft windows to prevent cellular phone users from using them on the planes. One could imagine that the cost of treating aircraft windows might be cost-prohibitive.
Kratz (U.S. Pat. No. 5,877,630), xe2x80x9cSystem and method for protecting an electronic device from electromagnetic radiation interferencexe2x80x9d teaches placing a detector inside sensitive circuitry. If the detector detects interfering radiation then it runs a test on the potentially effected circuitry to see if it was affected.
Lewis (U.S. Pat. No. 5,684,861), xe2x80x9cApparatus and method for monitoring cellular telephone usage.xe2x80x9d This is essentially a usage meter that would be tacked on to a rental cellular phone. The meter runs when its circuitry detects cellular phone transmission.
The system of Levi (U.S. Pat. No. 5,678,200), xe2x80x9cIndependent wideband RF transmission detector for cellular telephone,xe2x80x9d teaches a detector in a car which would shut off the stereo system when someone is using their hand-held cellular phone to make it easier to listen.
The invention of Pevler (U.S. Pat. No. 5,856,803), xe2x80x9cMethod and apparatus for detecting radio-frequency weapon use,xe2x80x9d teaches a military defense system which continuously looks for the spectral signatures of intentional radio frequency interference. At the end of the specification Pevler mentions radio frequency interference detecting and cellular phone number recording it. He does not say what to do with the number, how one would use it for prosecution, how one would identify the offending passenger, or how one would locate the offending passenger.
Frey (U.S. Pat. No. 5,444,762), xe2x80x9cMethod and apparatus for reducing interference among cellular telephone signals,xe2x80x9d teaches the use of an air cellular system which allows transmissions from the aircraft but is careful to use unused channels and is also careful to beam the signal in such a way that it will not interfere with ground base cellular systems.
Thus in spite of an obvious need, no one has taught any system for locating and identifying a cellular phone transmission within an aircraft.